1. Field of the Invention
The field of the invention relates to oil well drilling tools and in particular to an apparatus and method from cleaning scale and other materials from the interior walls of a pipe or similar structure.
2. Description of the Prior Art
There has long been a recognized need to wipe the internal walls of cylindrical members used in drilling operations, such as drill pipe, tubing and casing. Mud, oil and scale, if thus not cleaned from the interior surface of such cylindrical members, spills onto the platform floor when the pipe is tripped from the bore. The spillage of such liquids is both hazardous and commercially uneconomical. The hazard is particularly accentuated in situations where the drilling operation occurs in freezing temperatures such as in the arctic. Fluid and dripping mud will freeze on the platform surface and in between the drill pipe in a pipe stand. Even in temperate environments, the spillage of fluids from the interior of the drill pipe creates personel hazards and impediments to secure operation. Thirdly, the hydraulic fluid or drilling mud used in many present day applications includes additives which are regarded as pollutants or potentially environmentally hazardous if spilled in oceans, bays and at other drilling sites. According to current drilling practices, a rust treatment is often applied to the interior of the pipe when it is tripped. In order for such a treatment to be effective mud, oil and ooze must first be scraped from the interior to allow direct access of the rust preventative to the pipe interior.
One design for a prior art drill casing wiper is shown by Haggard, "Tubular Interior Wiper", U.S. Pat. No. 4,221,264 wherein a pair of flexible wipers 36 and 42 are employed to provide a scraping action.
Another wiper, employing a multiplicity of flexible disk elements 11 for wiping the pipe interior is shown by Cox, "Pipe Wiper", U.S. Pat. No. 2,740,480.
Hauk, "Apparatus and Method for Removing Scale and Wax from Oil Well Tubing", U.S. Pat. No. 3,285,778 shows a rigid mechanical scraper which is used in conjunction with compressed air to remove hard adhering materials from the interior of a drill pipe as it is removed from a bore hole.
Greenfield, "Pipe Cleaner", U.S. Pat. No. 3,101,499 shows a hammering mechanism which is lowered into well casing, which remains in place, in an attempt to hammer hardened scale and debris from the interior surfaces of perforated sections of the casing.
Finally Mcspaddan, "Method and Apparatus for Cleaning Wells", U.S. Pat. No. 2,876,842 shows a prior art method where a plug of petroleum ceresin wax is used to remove scaled deposits from drill pipe as opposed to a mechanical scraping or hammering element.
Each of the prior art attempts to provide a cleaning mechanism to the interior of pipe in drilling operations suffers from the defect that uniform and efficient cleaning or scraping action is dependent upon a substantially uniform interior diameter of the pipe. As a practical matter, this is not the case. Cylindrical members, where they interconnect, for example, will have a reduced diameter. In those situations where prior art mechanisms are incapable of compressing through reduced diameter sections, such as in the mechanism shown by Hauk, the scraper can be used to clean only one section of pipe at a time. In other cases where the scraping element is capable of resiliently compressing to thereby allow the tool to pass through a restricted section, the increase in softness of the scraping element thus required inherently detracts from the rigidity of the scraping element in that portion of the drill pipe having a normal inner diameter. In other words, if the scraping element is soft enough to squeeze through a restricted joint section, it was often soft enough to also be deformed by a harder deposit of wax, scale or tar elsewhere on the pipe interior.
Therefore, what is needed is some type of drill pipe wiper which is capable of passing through multiple sections of drill pipe and yet capable of providing a uniform and strong scraping action throughout those portions of the drill pipe having a normal inner diameter.